Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/54—Polycondensates of aldehydes
  • C08G18/542—Polycondensates of aldehydes with phenols
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
  • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
  • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • B22C1/2273—Polyurethanes; Polyisocyanates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/10—Esters; Ether-esters

Definitions

• casting molds and cores of any considerable size are made from material mixtures containing a grainy base (in most cases sand) mixed with a polyurethane-based, cold hardening binder system.
• a binder system is composed of polyisocyanates with at least two NCO groups in the molecule and polyols with at least two OH groups in the molecule as reaction partners, as well as a tertiary amine or in some cases a chelate compound as an accelerator.
• the accelerator will be added to the mixture either (a) together with the other ingredients of the binder system immediately before the mixture is to be used, or (b) only after the mixture, made up without the accelerator, has been put into a casting box and the mixture in the box is then treated with a gaseous tertiary amine accelerator.
• a binder system of this sort generally also includes a solvent, especially when one or both reaction partners are present in a higher molecular form such as prepolymers.
• a solvent especially when one or both reaction partners are present in a higher molecular form such as prepolymers.
• resins of condensation made of phenols or phenol-related compounds with aldehydes are quite well-suited polyols, which regularly require a solvent on account of their relatively high molecular weight.
• the solvent does not participate in the reaction between the polyisocyanates and the polyols to form urethanes, it nevertheless exerts an influence on the course of the reaction, which is probably related to the fact, among others, that the two reaction partners have varying degrees of compatibility with the various types of solvents.
• polar solvents are well suited for phenol resins and similar polyols but less compatible with polyisocyanates while the opposite is true of non-polar solvents.
• mixtures of polar and non-polar solvents are normally used, the proportions being adjusted to suit the particular binder system used.
• the individual ingredients of this mixture should not have too low a boiling point so that the solvent does not lose its effectiveness too soon through evaporation.
• non-polar solvents aromatic hydrocarbons which are usually in the form of mixtures with a boiling point above ca. 150° C. (at normal pressure) are preferred; and for polar solvents, aliphatic and cyclic ketones, fatty acid esters, acetals or ketals, glycol esters, glycol ether esters, glycol diethers and similar types of compounds having a sufficiently high boiling point have been used.
• phthalic acid dialkylesters preferably o-phthalic acid
• Such phthalic acid esters are quite odorless, if not completely so. They have the additional advantage that they are more compatible with polyisocyanates than, for example, isophoron (a cyclic ketone frequently used as a solvent) and therefore lead to casting forms with somewhat better characteristics.
• isophoron a cyclic ketone frequently used as a solvent
• their compatibility with polyisocyanates is still not optimal, and they have the additional disadvantage that they crack easily during the casting process, which leads to sublimation with a lot of smoke and correspondingly strong smell.
• the invention has the purpose of creating an odorless polar solvent for a polyurethane-based binder system for material mixtures used in the production of casting molds and cores, which will avoid the disadvantage of the phthalic acid dialkyl esters with regard to thermal stability during casting and will also improve the characteristics not only of the material mixture but also of the casting forms made from it.
• the invention achieves this by means of a solvent consisting of or containing esters having as their acid component either an aliphatic dicarboxylic acid with from six to twelve carbon atoms or a benzene polycarboxylic acid with three or more COOH groups, and having as their alcohol component an aliphatic, cyclo aliphatic, arylaliphatic or aromatic alcohol with from six to thirteen carbon atoms.
• Typical examples of the acid components of the group of esters lying in this range are the radicals of the aliphatic dicarboxylic acids adipinic acid (6 carbon atoms), suberinic acid (8 carbon atoms), azelaic acid (9 carbon atoms), sebacinic acid (10 carbon atoms) and decandicarboxylic acid (12 carbon atoms), as well as the radicals of the benzene polycarboxylic acids trimellitic acid (3 COOH groups attached to the benzene nucleus) and pyromellitic acid (4 COOH groups attached to the benzene nucleus).
• the alcohol components typical examples are all the aliphatic alcohols with six to thirteen carbon atoms, i.e., from hexylalcohol to tridecylalcohol, as well as cyclic, arylaliphatic and aromatic alcohols like cyclohexyl alcohol, cyclooctyl alcohol and benzyl alcohol, and in some cases alcohols with additional ether bridges, like butoxyethyl alcohol.
• the solvents specified in the invention need not consist of only one of the esters lying in the range of the invention, but may also be mixtures of different esters in this range.
• the solvents defined by the invention can be chosen from one or several of the following particular esters, which have been shown to be very appropriate: bis-(2-ethylhexyl)-adipate (DOA), di-n-nonyl-adipate and di-isononyl-adipate, di-n-octyl-adipate (DIDA), bis-[methylcyclohexyl]-adipate, bis-[methyl-cyclohexylmethyl]-adipate, benzyl-octyl-adipate, bis[butoxyethyl]-adipate, di-n-hexyl-azelate (DHAZ), tetrakis-[2-ethylhexyl]-pyromellitate, trisisooctyl-trimellitate, tris-octyl-trimellitate, bis-2-ethylhexylsebacate, di-n-octyl
• the solvents specified in the invention are odorless and nontoxic, so they fulfill the demands for environmental protection on the job. Also, their thermal stability is very high, and their rate of evaporation is practically nil. But above all, they improve the characteristics of the mold material and the molds made from it to a considerable degree, which is especially striking in the case of the gas hardening process.
• the solvents specified by the invention insofar as they are esters of an aliphatic dicarboxylic acid, have a relatively high number of carbon atoms, as well as a comparable number of carbon atoms in the two components; and the benzene polycarboxylic acids have three or more ester groups attached to the benzene nucleus.
• the esters used according to the invention have-despite the consistently higher number of ester groups in the molecule--a strongly hydrophobic, non-polar molecular structure, in which the polar effect of the ester groups is largely screened off by the hydrophobic radicals lying on the outside.
• esters having components with long chains which are not in the range of the invention do not have the positive effects of the solvents specified by the invention.
• the range of solvents specified by the invention is limited below by the fact that success does not occur if one of the two components has fewer than six carbon atoms.
• the upper limit is established by the fact that esters with more than twelve or thirteen carbon atoms are as hard as wax.
• the high thermal stability of the solvents specified by the invention in connection with their high boiling points delays the moment of disintegration in casting and thus increases the thermal load the molds are capable of bearing. Thus not only are problems arising from undesirable cracking avoided, but there is also an improvement of the casting surface, especially in the case of cast iron. Besides that, the solvents specified by the invention do not evaporate so that even in storage of cores or other molds which are being hardened by the gas hardening process, the solvents remain available to take on energy when used in casting.
• the general stability of molds produced by the use of the solvents specified by the invention is quite excellent and in any case better than that attainable with previously used solvents.
• two other factors should be especially pointed out, however, which play an important role in the gas hardening process, namely, the sand-life and the permanence of the hardened cores.
• Sand-life is the length of time in which a material mixture which has been prepared but not yet treated with the accelerator can be stored and remains useful.
• Use of the solvents specified in the invention gives sand-lives of five hours or more, after which time the forms are not as strong as they were initially but still quite adequate for casting. Such long sand-lives have not been possible with previously known solvents.
• the hardened molds are also capable of extended storage. While with the use of previously known solvents the stability falls off after reaching a maximum, especially when the humidity is high, molds made with a solvent specified by the invention do not show this phenomenon.
• Another surprising advantage of this invention is that when it is used with mixtures for the gas hardening process, a considerably smaller amount of gaseous tertiary amine is required. This reduced consumption of amine can be as much as 50% depending on the particular resin and solvent used.
• the solvents specified by the invention can be used alone but it is preferable to use them mixed with non-polar solvents of the usual types, particularly with aromatics having a high boiling point.
• the portion of such a solvent mixture which consists of solvents as specified by the invention can be anything in excess of 10% by weight and it is preferably between 10% and 60% and is chosen to suit the particular resin in question.
• the prepared resin solution can, in any case, have a solid content of from 40% to 60% by weight.
• the material mixtures produced in this way were made into mold shapes and hardened by treatment with gaseous triethylamine for one second. Finally, they were rinsed with air for ten seconds.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Mold Materials And Core Materials (AREA)
• Polyurethanes Or Polyureas (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (3)

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Citations (6)

Family Cites Families (2)

• 1977
  • 1977-12-31 DE DE2759262A patent/DE2759262C2/de not_active Expired
• 1978
  • 1978-03-09 CH CH257278A patent/CH634764A5/de not_active IP Right Cessation
  • 1978-05-30 US US05/910,283 patent/US4231914A/en not_active Expired - Lifetime
  • 1978-09-01 IN IN965/CAL/78A patent/IN149991B/en unknown
  • 1978-10-02 FR FR7828811A patent/FR2413152A1/fr active Granted
  • 1978-12-20 AT AT0911178A patent/AT372023B/de not_active IP Right Cessation
  • 1978-12-27 JP JP16023978A patent/JPS5497529A/ja active Pending
  • 1978-12-28 IT IT31376/78A patent/IT1102782B/it active
  • 1978-12-28 ES ES476400A patent/ES476400A1/es not_active Expired
  • 1978-12-28 AR AR275019A patent/AR219572A1/es active
  • 1978-12-28 CA CA000318784A patent/CA1120169A/en not_active Expired
  • 1978-12-29 BR BR7808620A patent/BR7808620A/pt unknown
  • 1978-12-29 GB GB7850285A patent/GB2013695B/en not_active Expired
• 1979
  • 1979-01-03 MX MX176093A patent/MX155087A/es unknown

Patent Citations (6)

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